High tension air blast circuit breaker



Aug. 16, 1960 R. SCHULZ HIGH TENSION AIR BLAST CIRCUIT BREAKER Filed Sept. 11, 1958 Mii.

United States Patent Hace 2,949,521

Patented Aug. 16, 1960 HIGH TENSION AIR BLAST CIRCUIT BREAKER Richard Schulz, Friedberg, Hesse, Germany, assignor to Allmnna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a Swedish corporation File-d Sept. 11, 1958, Ser. No. 760,357

Claims priority, application Germany Sept. 12, 1957 2 Claims. (Cl. 200-148) The present invention relates to a high tension air blast circuit breaker having its breaking gap arranged inside a compressed air container, which is under operating pressure at least When the breaking gap is open. If the operating pressure falls due to damage to the compressed air container, an unintentional closing or opening of the breaking gap of this breaker can occur, if the movable contact is held in its position by the operating pressure. This has to be avoided in any case. If the breaker is provided with a lplurality of series` connected breaking gaps per pole, the other breaking gaps can still be operated by blocking the supply line for the compressed air to the damaged breaking gap. But if the breaker is only provided with one or two breaking gaps per pole, a special safety measure is necessary.

In order to avoid that, in high tension air blast circuit breakers with a compressed air container enclosing the breaking gap and having the contacts under operating pressure at least in the open position, a decrease of the electric strength of the breaking distance may occur witha decrease in the operating pressure, the counter-contact belonging to the movable contact is not moved at normal operating of the breaker, but according to the invention automatically changes its position at a predetermined decrease of the operating pressure in the air container, so that the breaking distance is increased. For example, therefore, an open breaking gap, .the movable contact of which is kept in its position by the operating pressure, can never be closed again at an unintentional decrease in the operating pressure, as the counter-contact then has moved away from the movable contact to such an extent that there is a sutlicient insulating distance between the contacts even with the absence of compressed air. It can be arranged so that the counter-contact, which is not moved at normal operating of the breaker, is kept in its position against the force of a spring by a piston influenced by the operating pressure. If the operating pressure vanishes, the countercontact is moved in the direction from the movable contact by the spring force and thus the breaking distance is increased. Suitably the counter-contact, which is not moved at normal operating of the breaker, may be latched in its normal position in order to get a certain safety when operating the breaker. This latching is necessary in the closed position for avoiding that at decreasing air pressure an arc is drawn by the countercontact, which arc could not then be extinguished. In the open position the block can for instance be removed by the operating or blast air or by the movable contact being in its open position.

In a circuit breaker the movable contact of which is held by the operating pressure in its open position, in which also the counter contact is unlatched, the arrangement has to be such that at decreased operating pressure in the compressed air container the counter-contact starts its movement earlier than the movable contact being in its open position, in order to prevent that the movable contact on its movement to its closed position touches the counter-contact. When the counter-contact has .taken up a position increasing the breaking distance, itis advantageously latched, in order to avoid an undesired closing of the breaker at an unforeseen increase of the operating pressure. According to the design of the circuit breaker also the operating mechanism of the lcounter-contact can be mechanically or pneumatically connected to a fault indicator.

The iigures serve for explaining the invention and show schematically a possible design of the breaker in the closed, open and latched position. Fig. l shows the breaking gap in the closed position. The support 1 carries the compressed air container 2, in which there are arranged the movable contact 3 and `the countercontact 4. The movable contact 3 is operated by a mechanism identical to that described in the patent to Forwald, No. 2,803,724. The contact 3 is held in the closed position by the spring 5, as long as the space '6 is under pressure. The breaker opens when the space 7 is supplied with operating air, and the piston 8 and the differential piston 9` are moved downwards, the valve 10 is closed and the valve 11 is opened. Through the latter air can stream from the space 2 through the movable contact 3 to the open air through the opening 12. The valve 10 closes the channel 13 leading to the container 2 and connects the space 6 with the outer space over the channel4 14. Now the contact 3 is moved upwards and the arc is exposed to the blast air and is extinguished. The opening 15 in the differential piston 9 causes an equalisation of the pressure on both sides of the piston so that the piston is moved back to its starting position by the spring 16 and the movement of the contact 3, so that the valve 11 closes again.

In the open position, Fig. 2, the contact 3 is held in its position against the force of the spring 5 by the compressed air in the space 2. If in the open position the operating air is removed from the space 7 for the purpose of closing the breaker, the piston 8 is moved upwards and opens the valve 10, so that the space 6 is connected with the space 2 through the channel 13. Thus the contact 3 is moved downwards into the closed position due to the force of the spring 5 (Fig. l). The counter-contact 4 is displaceably arranged and attached to the pipe 17, which at one end is widened to form a piston. Thus the counter-contact 4 forms with the piston 18 a differential piston. A space 25 on the upper side of the piston 18 is in communication with the open air through the opening 24 and the space 19 below the piston 18 communicates with the compressed air container 2, through the pipe 17 and the opening 23. Thus the piston 18 is biased upwards by the compressed air in the space 19 against the force of the spring 20 and held in its` normal operating position as long as the air pressure in the container 2 and space 19 is held above a predetermined value. In this position the piston 18 is latched by the hook pin 21. The latter is lifted by the `operating air from the pipe 22, when on opening of the breaker the space 7 is supplied with operating air. The position of the counter-contact 4 is unchanged, as the space 19 is connected with the air container 2 through the pipe 17 and consequently compressed air influences the piston 18.

It in the closed position (Fig. l), due to some reason, the air pressure in the container 2 decreases, the countercontact 4 remains in its latched position, as the pipe 22 is not lledwith operating air and the hook pin 21 is still in the indicated position. Thus, if the breaking gap is in its closed position, it cannot open if the compressed air in the container 2 vanishes.

In the open position of the breaker (Fig. 2), on the other hand the pipe 22 is filled with compressed air so that the hook pin 21 does not latch the piston 18. If now the air pressure, due to some reason, decreases in the container 2, the counter-contact 4 is moved downwards by the force of the spring 20 (Fig. 3), before the piston 18 is latched by the hook pin 21, as the cornpressed air escapes more slowly from the pipe 22 than from the container 2. Also the movable contact 3 is moved downwards by the spring 5. As, however, the

movement of the `counter-contact 4 is faster than that of the movable contact 3, a sufficiently large distance between the contacts is maintained,'thus preventing the current circuit from closing again if the compressed air vanishes in the open position of the breaker.`

in the lower end position of the piston 1S, Fig. 3, the 'nook pin will fall down after that the pressure of the operating air also in the pipe 22 gradually has decreased, and the differential piston 18 is latched in this position. Thus the counter-contact 4 cannot move back if the air pressure in the container 2 increases again. A fault signal or an indicating device can be actuated by the movement of the piston 18.

i claim as my invention:

l. A pneumatically operated circuit breaker comprisV ing a first movable contact, a second movable Contact, a container enclosing said contacts, said first contact being movable between a first and a second position, said second Contact when said first contact is in its rst position being movable between a first engaged position and a second disengaged position with respect to said first contact, said first contact in its second position being at an insulating distance from said second contact even when said `second contact is in its first position, the said container being filled with compressed air at 4. least when said second contact is in its second position, pneumatic operating means responsive to a predetermined pressure condition in the container' for moving said first contact to its second position, and latch means arranged to latch said first contact in its first position when said second contact is in its first engaged position.

2. A pneumatically operated circuit breaker comprising a first movable contact, a second movable contact, a container enclosing said contacts, said rst contact being movable between a first and a second position, said second contact when said first contact is in its first position being movable between a first engaged position and a second disengaged position with respect to said first contact, said first contact in its second position being at an insulating distance from said second contact even when said second contact is in its first position, the said container being filled with compressed air at least when said second contact is in its second position, pneumatic operating means responsive to a predetermined pressure condition in the container -for moving said first contact to its second position, and a latch device arranged to latch the first contact in its second position.

References Cited in the file of this patent UNITED STATES PATENTS 2,803,724 Forwald Aug. 20, 1957 FOREIGN PATENTS 1,003,321 Germany Feb. 28, 1957 337,508 Great Britain Nov. 6, 1930 394,620 Great Britain June 29, 1933 594,386 Great Britain Nov. 10, 1947 

